Atrial fibrillation is a condition in the heart in which the generation of abnormal electrical signals causes irregular beatings of the heart. A proven protocol for successfully treating this condition is open heart surgery (sometimes referred to as the “maze” procedure) where several long (i.e. approximately 2-10 cm) lesions are created in the endocardium within the upper chambers of the heart (“atria”). These lesions block the flow of excess electrical impulses within the atria and allow the impulse from the sinus node to properly regulate heart contraction.
However, because open heart surgery is highly invasive and requires a lengthy patient recovery period, alternative methods for making lesions have been recently explored. One such alternative is the use of ablation catheters that includes one or more electrodes.
Typically, an ablation catheter is advanced into the heart via the patient's vessels. When the electrodes are placed in the desired position within the heart chamber, radio frequency (“RF”) energy is supplied to the catheter thereby burning lesions into the endocardium.
Initial designs for ablation catheters generally comprised an elongated shaft with an electrode mounted at the distal end. Either point and linear lesions could be formed with these catheters by manipulating the placement of the tip. However, because of the tendency for the tip electrode to overheat and to lift off the tissue surface during ablation, creating suitable lesions using these catheters have been difficult.
New catheter designs attempted to mitigate these disadvantages. One improvement is the addition of a mechanism to cool the tip electrode during use to minimize the risk of embolism from overheated blood. Although these catheters mitigate some of the overheating problems, hotspots on the tip or in adjacent tissue may still develop.
Accordingly, while some conventional catheters are effective for cardiac ablation, further advances could be beneficial.